The influence of Mn deposited on a Pd(100) surface on the adsorption, dissociation and desorption properties of NO has been studied using infrared reflection absorption spectroscopy ( IRAS), temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). On the Mn/Pd(100) surface, only the NO adsorbed on the Pd was observed at 320 K. Thermal dissociation of NO did not occur on the clean Pd( 100) surface; it did occur, however, on the Mn/Pd( 100) surface at 320 K. A Pd - Mn alloy was formed by deposition of Mn onto the Pd( 100) surface; the formation of the Pd - Mn alloy was correlated with the activity of NO dissociation, assuming that it was the active site for this dissociation. The oxygen produced from the dissociation of NO was found to destroy the Pd Mn alloy, forming MnOx. No desorption of oxygen from MnOx on Pd(100) was observed below 1200 K.